What is a term for a server that is functioning 24/7?


What is a term for a server that is functioning 24/7?

If we have some critical servers that have to be running 7 days a week, 24 hours a day and they can't be down even for one second, what is this particular type of server called in English?
Example sentence:

Our servers must be flawless; they must be _____.

Does the term productive suit?


Answer 1:

Critical services have their own terminology for this that lessens the ability to weasel around phrases like “24/7”, “round-the-clock”, “Mission critical”, etc.

It’s the “Nines” system and is common in legal contracts for “High availability” services.

Calculate “Nines” by taking the percentage of uptime over total time. For example, if a server was up for only 9 out of 10 seconds, that’s 90% or “One nine”.

“Five nines”:

The common “Five nines” is 99.999% which still allows 6 seconds of downtime per week.

To get to less than 1 second per week, you need to guarantee “Six nines” or more — which is a herculean task in the long term. (Even more-so if you don’t use the standard “Unplanned” weasel word.)
For example, Google and Microsoft typically only promise “3 nines” (and frequently fail even that), which is a whopping 10 minutes down per week.

Answer 2:


lasting all day and all night.

  • ‘round-the-clock surveillance’
  • ‘He has hired 500 more workers and this month is adding a third shift for
    round-the-clock production – a first in auto manufacturing history.’

Oxford Dictionaries

Answer 3:

If the server cannot be down for even one second, the downtime it experiences must be zero seconds.

In other words, it is a zero-downtime server.

The term zero downtime
seems to be widely used in the industry, for example
here and here.

Answer 4:

I would go with high-availability.

Most, if not all servers, need some down-time when updates and patches are installed.

Answer 5:

“what is this particular type of server called in English”

I would go with either continuously available or mission critical. These terms better suit the specific context of a system or set of systems that support or underpin a goal or task. Personally I think the first specifically describes the type of system you are asking about.

Answer 6:

A 100% uptime server:


Time during which a piece of equipment (such as a computer) is
functioning or able to function

— Merriam-Webster

Here are some examples of the phrase in use: –

Uptime is never 100%. A world of factors conspire against 100% uptime,
and can potentially disrupt the flow of bits from the server to your
browser. But despite the number of factors, most hosting companies are
at or above 99.9% uptime.

WP Engine

What we mean when we say 100% uptime is that there will never be any
downtime in the time period starting now and extending to infinity.


Answer 7:

Usually such computers nodes are a group of machines in such a way that either one of these could be down, the group as a whole keeps running and the intended service is delivered. Such systems are highly available systems.

Answer 8:

The answer in your title is rock solid.

The answer in your question is mission critical.

The Free Dictionary:

rock-solid or rock solid
2. extremely reliable

The Free Dictionary:

Mission critical
Mission critical refers to any factor of a system (equipment, process, procedure, software, etc.) whose failure will result in the failure of business operations. That is, it is critical to the organization’s ‘mission’.

Answer 9:

If you depend on a continuously running server which must not be down for even one second, the term is time bomb.

Sooner or later, it will be down for more than one second.

Machines that cannot be down for any reason for more than a second require special hardware with redundancy for fault tolerance, a special operating system, running in dedicated data center.

Answer 10:

I suppose you could use “Continuous”, but I believe the word you’re looking for is


Which means:

endless or apparently endless